vhost: remove unused feature bit

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

include/uapi/linux/vhost.h

@@ -172,8 +172,6 @@ struct vhost_memory {
 #define VHOST_F_LOG_ALL 26
 /* vhost-net should add virtio_net_hdr for RX, and strip for TX packets. */
 #define VHOST_NET_F_VIRTIO_NET_HDR 27
-/* Vhost have device IOTLB */
-#define VHOST_F_DEVICE_IOTLB 63
 
 /* VHOST_SCSI specific definitions */